Method for laying composite tape

ABSTRACT

A composite member and an associated method for forming the composite member are provided. The composite member is formed of a plurality of elongate tapes. Each tape is disposed a path defined by a plurality of natural path segments, each of which defines a non-natural offset angle relative to the adjacent segments.

This application claims the benefit of U.S. Provisional Application No.60/615,895, filed Oct. 5, 2004, which is incorporated herein in itsentirety.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to the manufacture of composite structuresand, more specifically, to an apparatus and associated method for layingor disposing elongate tapes in a contoured configuration to form thecomposite structures.

2) Description of Related Art

Composite members are typically formed of a reinforcement material thatis disposed in a matrix material. For example, the reinforcementmaterial can be a fibrous material such as graphite, and the matrixmaterial can be a resinous polymer material. According to oneconventional manufacturing method, the composite material is disposed inthe desired shape of the composite member by laying a plurality ofelongate composite tapes to progressively build the layers of themember. An automated operation for forming the composite member canbegin by using a contoured tape laying machine (CTLM) to dispose a firstlayer of tapes onto a mandrel that defines the shape of the compositemember. The CTLM includes a roll or other supply of the tape, which isdispensed onto the mandrel with a tape placement head that guides thetapes onto the mandrel in the desired configuration. That is, the tapeplacement head provides relative movement between the mandrel and thehead so that the head moves over the surface of the mandrel. The headusually makes repeated passes over the mandrel in a defined patternuntil the mandrel is entirely covered, and additional layers of the tapeare built up by continued passes of the head over the surface. Acompaction roller presses the tape against the mandrel or the previouslydisposed layers of tape to facilitate adhesion of the multiple layers ofthe tape.

This conventional CTLM can accurately place the tapes, and the automatedprocess can increase the speed at which the composite members can beformed. In addition, the CTLM is typically able to lay the tapes in avariety of configurations corresponding to the surface of a selectmandrel to thereby form the composite member to the desired shape. Inone conventional method for manufacturing a complex contoured surface, afirst tape is disposed across the mandrel along a natural path, i.e., acourse along which the tape can be disposed substantially flat againstthe mandrel with minimal stressing or wrinkling of the tape. For acontoured mandrel, the natural path is typically curved. After the firsttape is disposed along a natural path, subsequent tapes are disposedalong natural paths that extend across the mandrel in a similardirection as the first tape, i.e., generally parallel to the first tape.However, due to the complex contour of the mandrel, the natural paths ofthe adjacent tapes are not parallel along their entire lengths.Typically, the tapes are disposed about as close as possible whileavoiding any overlapping of adjacent tapes (i.e., “laps”). Thus, theedges of adjacent tapes that are disposed along natural paths definespaces or “gaps” therebetween, and the size of the gaps can vary alongthe lengths of the tapes. In some cases, the CTLM may be unsuitable forforming the member.

Therefore, there exists a need for an apparatus and method for disposingtapes to define complex configurations while reducing or minimizing thelaps and/or gaps defined by adjacent tapes and for doing so withoutsubstantially wrinkling the disposed tapes.

SUMMARY OF THE INVENTION

The present invention provides a method of forming a composite memberand an associated composite member and apparatus. The method can be usedto dispose composite tapes to form a composite member having a complexconfiguration. The method can reduce or minimize the occurrence of laps,gaps, wrinkling, and/or other undesired nonuniformities in the tapes.

According to one embodiment, the present invention provides a method inwhich a contour surface corresponding in shape to a desired contour ofthe composite member is provided for supporting a plurality of elongatetapes in a substantially parallel configuration. Each tape, whichincludes a plurality of reinforcement members disposed in a matrixmaterial, is disposed along a path defined by a plurality of naturalpath segments. Each segment defines a non-natural angle relative toadjacent segments of the path, and each tape defines a plurality ofconsecutive portions corresponding to the natural path segments, suchthat a transverse edge of each elongate tape is disposed within apredetermined offset distance interval from an adjacent one of thetapes. Typically, the tapes are disposed on the surface substantiallywithout wrinkling of the tapes.

A configuration of each path can be determined by determining thecontour of the surface, determining a first path across at least aportion of the surface, and calculating a configuration of each naturalpath segment of a second path adjacent the first path, a first end ofthe each natural path segment defining an offset angle relative to anadjacent segment such that a second end of each natural path segmentdefines a predetermined offset distance from the first path, the offsetdistance being within the predetermined offset distance interval. Forexample, the natural path segments can be calculated with the offsetangle of each natural path segment being less than a predeterminedmaximum offset angle so that the elongate tapes are configured to bedisposed without wrinkling. Further, the natural path segments can becalculated with the offset distance interval of the second end of eachnatural path segment being approximately equal to a target distance thatis less than the maximum of the predetermined offset distance interval.

More particularly, the configuration of a first one of the natural pathsegments of the second path can be calculated at a point partiallybetween opposite ends of the second path, and the configuration of thesuccessive natural path segments of the second path can be calculated inopposite directions from the first one of the natural path segments,with the second end of each successive path segment defining the firstend of a successive one of the path segments. Prior to calculating theconfiguration of the first one of the natural path segments, aconfiguration of a natural path adjacent the first path can becalculated, and a portion of the natural path adjacent the first pathdefining a minimum transverse distance therebetween can be determined.Thus, the configuration of the first one of the natural path segmentscan include calculating the configuration of the first one of thenatural path segments at a point corresponding in position to theportion of the natural path defining the minimum transverse distance.

The elongate tapes can be disposed from a supply roll of an automatedtape laying device and pressed against the contour surface with acompaction device. Each tape can be disposed in a plurality of portions,each portion being at least about a length of the tape supplied andsupported between the supply roll and the compaction device of theautomated tape laying device.

The present invention also provides, according to another embodiment, acomposite member that includes a plurality of elongate tapes disposed ina generally parallel configuration to define a contour surface. Each ofthe tapes, which include a plurality of reinforcement members disposedin a matrix material, is disposed along a path defined by a plurality ofnatural path segments. Each segment defines a non-natural offset anglerelative to adjacent segments of the path, and each tape defines aplurality of consecutive portions corresponding to the natural pathsegments so that a transverse edge of each elongate tape is disposedwithin a predetermined offset distance interval from an adjacent one ofthe tapes. The elongate tapes can be disposed without wrinkling. Forexample, the adjacent portions of each tape can define non-naturaloffset angles that are no more than about 4° or no more than about 0.5°.The tapes can define various numbers of portions disposed along naturalpath segments, typically depending on the length of the tapes. Forexample, each segment (and, hence, each consecutive portion of thetapes) can define a length that is between about 3 inches and 6 feet,such as between about 6 inches and 3 feet, with the adjacent portions ofeach tape defining the non-natural offset angles therebetween.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is an elevation view schematically illustrating an apparatus fordisposing an elongate tape during formation of a composite memberaccording to one embodiment of the present invention;

FIG. 2 is a perspective view illustrating a composite member formedaccording to one embodiment of the present invention;

FIG. 3 is a perspective view illustrating a composite member duringmanufacture according to one embodiment of the present invention;

FIGS. 4-8 are plan views schematically illustrating the paths alongwhich elongate tapes are disposed for forming a composite memberaccording to one embodiment of the present invention;

FIGS. 9-11 are plan views schematically illustrating the paths alongwhich elongate tapes are disposed for forming a composite memberaccording to another embodiment of the present invention; and

FIG. 12 illustrates a composite tape disposed along the path of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

Referring now to the drawings and, in particular, to FIG. 1, there isschematically illustrated an apparatus 10 for disposing an elongate tape12 during formation of a composite member 14 according to one embodimentof the present invention. The apparatus 10 can be used to form compositemembers 14 of a variety of materials and having various configurations.In particular, the apparatus 10 can be used to dispose one or moreelongate tape 12 that includes a reinforcement material disposed in amatrix material. The tapes 12 can be provided in various sizes andshapes, typically being long rectangular strips having a width of 3inches, 6 inches, or 12 inches. Typically, the reinforcement material isa plurality of fibrous members such as fibers, strands, braids, woven ornonwoven mats, and the like of materials such as fiberglass, metal,minerals, conductive or nonconductive graphite or carbon, nylon, aramidssuch as Kevlar®, a registered trademark of E. I. du Pont de Nemours andCompany, and the like. Each tape 12 typically includes the matrixmaterial, in which the reinforcement members are disposed. In somecases, however, the tapes 12 can be formed without the matrix material,and the matrix material can be disposed separately. In any case, thematrix material can include various materials such as thermoplastic orthermoset polymeric resins. Exemplary thermosetting resins includeallyls, alkyd polyesters, bismaleimides (BMI), epoxies, phenolic resins,polyesters, polyurethanes (PUR), polyurea-formaldehyde, cyanate ester,and vinyl ester resin. Exemplary thermoplastic resins includeliquid-crystal polymers (LCP); fluoroplastics, includingpolytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP),perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), andpolytetrafluoroethylene-perfluoromethylvinylether (MFA); ketone-basedresins, including polyetheretherketone (PEEK™, a trademark of VictrexPLC Corporation, Thointons Cleveleys Lancashire, UK); polyamides such asnylon-6/6, 30% glass fiber; polyethersulfones (PES); polyamideimides(PAIS), polyethylenes (PE); polyester thermoplastics, includingpolybutylene terephthalate (PBT), polyethylene terephthalate (PET), andpoly(phenylene terephthalates); polysulfones (PSU); poly(phenylenesulfides) (PPS).

As discussed further below, the tapes 12 can be disposed to define adesired configuration of the composite member 14. In particular, thetapes 12 can be disposed to form members of various sizes and shapes.For example, the composite member 14 illustrated in FIG. 2 is a wing foran aircraft. In other embodiments, the composite members 14 can be usedas other airfoils, aircraft body panels, other members for aerospacevehicles and structures, structural members of automobiles, marinevehicles or other vehicles, and the like. In some cases, the compositemember 14 can define a complex geometry, e.g., one or more contours thatare curved about multiple axes, define bends, apertures, or otherirregular shapes, and the like.

The apparatus 10 can generally define a tape placement head that is usedto dispose the elongate tape 12 in a configuration corresponding to thedesired shape of the composite member 14. For example, as illustrated inFIG. 1, the apparatus 10 can dispose the elongate tape 12 onto a mandrel16, i.e., a tool with a contour surface 18 that is then imparted to thetape 12 and, hence, the composite member 14. It is appreciated thatvarious types of mandrels can be used, and the mandrel 16 can define avariety of contours. In particular, the surface 18 of the mandrel 16 candefine a complex contour on which it would be difficult or impossible todispose rectangular tapes without laps or gaps occurring between theadjacent tapes. Also, while it is generally described herein that thetape 12 can be disposed “on” the mandrel 16, it is appreciated that afirst layer of the tape 12 may be disposed directly on the mandrel 16and subsequent layers may be disposed on the prior layers.

The apparatus 10 includes a supply of one or more elongate tape 12,which is dispensed and disposed onto the contour surface 18. Forexample, the tape 12 can be supplied in a dispenser, such as a roll 20that is supported on a spool 22 mounted in the apparatus 10. In somecases, the dispenser can include multiple rolls or other supply devicesthat provide multiple tapes 12 to be simultaneously disposed on themandrel 16. Alternatively, a single tape 12 can be disposed in one ormore portions. For example, a single tape 12 can be severed intomultiple portions that are disposed successively on the mandrel 16, orthe single tape 12 can be disposed continuously on the mandrel 16 as asingle piece without being severed. That is, the “plurality of tapes” or“multiple tapes” referred to herein can be disposed as a single piece oftape that defines a plurality of adjacent elongate portions.

In the embodiment illustrated in FIG. 1, the spool 22 supporting theroll 20 is rotatably mounted so that the tape 12 can be dispensedtherefrom. The tape 12 is supplied from the roll 20 to a placement guidethat controls the placement of the tape 12 on the mandrel 16. Theplacement guide can be a roller 24, as shown, that is rotatably mountedso that the apparatus 10 can be moved over the surface 18 of the mandrel16 with the roller 24 in rolling contact therewith. Thus, the apparatus10 can apply a force via the roller 24 in a direction generally towardsthe mandrel 16 so that the compaction roller 24 exerts pressure on thetape 12 to press it against the mandrel 16 in a compaction region. Theroller 24 can also be adjustably mounted by mounts 27, which can adjustrelative to the rest of the apparatus 10 so that the roller 24 can applyvarying pressures against the tape 12 and mandrel 16 or otherwisecontrol the placement of the tape 12. While a compaction roller 24 isdepicted, other types of compaction devices may be utilized, such as acompaction shoe or a press.

The apparatus 10 is moved relative to the mandrel 16 by a drive assembly26, which is schematically indicated in FIG. 1. The drive assembly 26can include various drive devices such as pneumatic or hydraulicactuators, electrical motors or servos, and/or chain, gear, or shaftdrive mechanisms. The drive assembly 26 can be configured to move theapparatus 10 or the mandrel 16 to achieve the desired relative placementof the apparatus 10 relative to the mandrel 16 for disposing the tape 12over the surface 18 of the mandrel 16. Typically, the apparatus 10 ismoved generally linearly along the surface 18 of the mandrel 16 inmultiple passes, with one or more portions of the tape 12 being disposedin each pass. For example, the apparatus 10 can move from a first end 28of the mandrel 16 to an opposite end 30 to dispose one or more tape 12,then return to the first end 28 to start another pass in the samedirection to dispose additional tape 12 adjacent those tapes 12 disposedin the previous pass. Alternatively, the apparatus 10 can wrap one ormore tapes 12 in continuous passes around the mandrel 16, with theposition and/or direction being adjusted between each pass so that thetapes 12 are disposed in adjacent portions.

The apparatus 10 can also include various other components. For example,roller 32 can be used to guide the tape 12 through the apparatus 10. Anynumber of rollers 32, 34 can be provided, and in some cases, some or allof the rollers 32, 34 can be driven by a motor or other actuator tocontrol the motion of the tape 12. In addition, the apparatus 10typically includes a heating device 36 for heating the tape 12 and/orthe mandrel 16. The heating device 36 can be a laser, a laser diodearray, a hot gas torch, an electric heater, or the like. The heatingdevice 36 typically delivers sufficient energy to permit the tape 12,once subjected to the compaction forces, to adhere to the underlyingtape 12.

The heating device 36 can include multiple independent heating elements,such as multiple laser diodes that form an array. Each heating elementcan be coupled to a power source in a manner independent of the otherlaser diodes so that the operating power of each heating element can becontrolled independently of the other heating elements. One such heatingdevice is further described in U.S. Pat. No. 6,451,152 to Holmes, etal., entitled “Method for Heating and Controlling Temperature ofComposite Material During Automated Placement,” issued Sep. 17, 2002 andassigned to the assignee of the present application, and the entirety ofwhich is herein incorporated by reference. Further, as described in U.S.Pat. No. 6,451,152, the individual heating elements can be arranged sothat each is configured to heat a particular area or zone, which can bedefined by the tape 12, before and/or after being disposed on themandrel 16. Thus, by altering the operating power of one or more of theheating elements, the heating of a particular one of the tapes 12 or aparticular area of the tapes 12 can be controlled independently of theheating of other tapes 12. Non-uniform heating of the zones may bedesirable, for example, if the tapes 12 are not the same size or are notmade of the same materials and thus require different amounts of energyto attain their optimum temperature for placement. Also, differentamounts of heating may be desirable due to the geometry of the mandrel16.

The heating device 36 can electrically communicate with a controller 40configured to control the heating device 36. The controller 40 can alsoperform other functions, for example, functions integral to inspection,speed control, temperature and velocity sensing, defect marking, and thelike. For example, the apparatus 10 can have an inspection system 42that includes cameras, temperature sensors, pre-placement detectors,tack monitoring devices, and the like for monitoring the tape 12.Additionally, the apparatus 10 can include a marking device for markingdefects or other designated portions of the composite member 14.

Each of the elongate tapes 12 can be disposed along a modified path 50that is defined by a plurality of natural path segments. The term“natural path” refers to a geodesic curve, i.e., a curve which islocally straight with respect to the surface because its geodesiccurvature is equal to zero at every point. Geodesic curvature is aspecial kind of curvature, which can be defined in the context of acurve lying on a surface. Given a curve lying on a surface, at eachpoint where the curve touches the surface, a plane can be constructed,called the tangent plane, which is the best flat approximation to theset of neighboring points on the surface. If at a given point, thecurve, when projected (i.e. viewed) perpendicular to the tangent planeat that point, appears straight, then the curve has zero geodesiccurvature at that point. A geodesic curve (or natural path) has thisproperty at every point along its length. Given two distinct points on asurface, the shortest path between them is a geodesic curve.

Each modified path 50 according to the present invention includes aplurality of natural path segments that define non-natural offset anglesat the points where the segments join. That is, each segment of themodified paths 50 defines a natural path. However, if the modified pathis projected perpendicular to the tangent plane at a point where twoadjacent segments join, then the projected segments define an offsetangle at that projected point which is not zero. Thus, the modifiedpaths do not have geodesic curvature equal to zero at the points whereadjacent segments join, and hence are not natural paths.

Accordingly, with the tapes 12 disposed along the modified paths 50 ofthe present invention, each tape 12 defines a plurality of consecutiveportions, each portion corresponding to one of the natural pathsegments. Each segment of each path 50, and hence each portion of eachtape 12, can be linear or nonlinear. For example, the natural path overa planar portion of a surface is linear; however, the natural path overthe contoured mandrel 16 is nonlinear and can define curvature about oneor more dimensions depending on the configuration of the surface 18.

One method of determining the path 50 of each tape 12 for forming thecomposite member 14 is illustrated in FIGS. 4-8. FIG. 4 illustrates afirst path 50 a that corresponds to a centerline 52 a of a first one ofthe tapes 12, indicated individually by reference numeral 12 a. The tapethat is disposed first on the contour surface 18 for forming thecomposite member 14 is typically disposed along a natural path thatextends between the longitudinal ends 28, 30 of the mandrel 16 at aposition between transverse ends 29, 31 of the mandrel 16. For example,as shown in FIG. 3, the first tape 12 a can be disposed on the mandrel16 before any of the other tapes 12, and is disposed along a naturalpath. Subsequent tapes 12 are disposed generally parallel to the firsttape 12 a on either side of the first tape 12 a. The centerline 52 a ofthe first tape 12 a is indicated in FIG. 3 for purposes of illustrativeclarity. As shown in FIG. 3, the centerline of the first tape 12 adefines a three-dimensional curve, i.e., a line that curves aboutmultiple, nonparallel axes.

Referring again to FIG. 4, the path 50 a of the first tape 12 a isillustrated (corresponding to the tape's centerline 52 a) in a straightconfiguration for illustrative clarity, though the actual configurationof the path 50 a can be curved to correspond to the centerline 52 a ofthe tape 12 a as shown in FIG. 3. The first path 50 a can be a naturalpath, i.e., the path 50 of the tape 12 that is to be disposed first onthe contour surface 18. Alternatively, the first path 50 a indicated inFIG. 4 can be a segmented path that is calculated according to themethod described below. That is, the terms “first path” and “first tape”are used below for convenience to refer to a preceding tape for whichthe path 50 a has been calculated and used for reference in calculatingthe configuration of a second path 54 that is subsequent and adjacentthe first path 50 a, and along which a second tape is to be disposedadjacent the first tape 12 a. The tapes 12 can be disposed on thesurface 18 in various sequential orders. Further, FIGS. 4-8 do notillustrate the actual tapes 12. In fact, FIGS. 4-8 are indicative of thedetermination of the paths 50 of the tapes 12, and the paths 50 can bedetermined before some or all of the tapes 12 are disposed on themandrel 16. For example, the paths 50 of the tapes 12 can be determinednumerically, so that the tapes 12 can then be disposed according to thecalculated paths 50.

In order to determine a second path 50 b for the second tape 12,indicated individually by reference numeral 12 b, that is to be disposedproximate the first tape 12 a, a first point (or start point) 54 of thesecond path 50 b is defined at a transverse distance from the path 50 aof the first tape 12 a. In particular, the first point 54 is typicallypositioned transversely from the path 50 a of the first tape 12 a by adistance that is about equal to the width of the tapes 12. Thus, withthe first tape 12 a disposed along the first path 50 a and the secondtape 12 b disposed along the second path 50 b, transverse edges 56 ofthe tapes 12 a, 12 b are proximate one another. The centerlines 52 a, 52b of the tapes 12 a, 12 b can be spaced slightly more than the width ofthe tapes 12 to provide a small gap between the tapes 12. In particular,the first point 54 can be offset transversely slightly more than thewidth of the tapes 12 so that the tapes 12 a, 12 b define therebetweenan offset distance that is within a predetermined offset distanceinterval. The predetermined offset distance interval can be defined by aminimum offset distance, a maximum offset distance, and a target (ordesired) offset distance that is between the minimum and maximumdistances.

The configuration of the second path 50 b in a direction generallytoward one of the ends 28, 30 of the surface 18 is then determined in aplurality of natural path segments 58 a, 58 b, 58 c. As shown in FIG. 6,the first segment 58 a extends from the first point 54. That is thefirst end of the first segment 58 a is defined by the first point 54,and the opposite, second end of the segment 58 a is defined by asubsequent point that is also positioned transversely from the firstpath 50 a by a distance within the predetermined offset distanceinterval. As shown in FIGS. 7 and 8, the second point of each segment 58a, 58 b, 58 c is the first point of the successive segment 58 a, 58 b,58 c along the same path 50. The configuration of each segment 58 a, 58b, 58 c can be determined using an iterative process, in which thesecond end of each segment 58 a, 58 b, 58 c is calculated such that eachsegment 58 a, 58 b, 58 c has a uniform or fixed segment length, and thesecond end of each segment 58 a, 58 b, 58 c (as defined by thecenterline 50 b of the segment 58 a, 58 b, 58 c) is maintained withinthe predetermined offset distance interval from the first path 50 a.Further, the first and second tapes 12 a, 12 b can be made to define agap along their lengths that is also within the predetermined offsetdistance interval. For example, the second end of a respective one ofthe segments 58 a, 58 b, 58 c can first be assigned a coordinateposition that is transversely positioned from the first path 50 a by thetarget offset distance, as shown in FIG. 5. The contour of the segment58 a, 58 b, 58 c (and, hence, the corresponding portion of the tape) isthen determined so that the segment 58 a, 58 b, 58 c follows a naturalpath along the surface 18 between the first and second points. Aconfiguration of a natural path between two points on a contour surfacecan be determined using various known methods, such as by mathematicallymodeling the configuration of the tape 12 according to the surface 18.The gap between the first and second tapes 12 a, 12 b is determinedalong the entire length of the segment 58 a, 58 b, 58 c. If the gap isoutside the interval, i.e., less than the minimum or greater than themaximum offset distances, then the direction of the segment 58 a, 58 b,58 c is modified slightly (FIG. 6). That is, the segment 58 a, 58 b, 58c is made to extend from the first point 54 at a slightly differentangle. Although the segment extends from the first point at a slightlydifferent angle, the segment 58 a, 58 b, 58 c will still define anatural path between its ends. The orientation of the segment 58 a, 58b, 58 c is typically modified a minimal amount so that the entiretransverse edge 56 of the segment 58 a, 58 b, 58 c defines a gap withthe first tape 12 a that is within the predetermined offset distanceinterval.

Thus, after the configuration of the first segment 58 a of the secondpath 50 b is determined, the configuration of successive segments 58 b,58 c extending from the first segment 58 a toward the end 30 of thecontour surface 18 are determined similarly in a sequential manner, asshown in FIG. 8. Further, the configuration of the second path 50 b issimilarly determined in a direction from the first point (start point)54 toward the opposite end 28 of the contour surface 18, as indicated inFIG. 8, including segments 58 d, 58 e, 58 f. Each path 50 can includeany number of segments, and, hence, each tape can define any number ofcorresponding consecutive portions. Each of the segments, referred tocollectively by reference numeral 58, defines a natural path, and thesegments 58 are defined such that, with the centerlines 52 of the tapes12 disposed according to the paths 50, the transverse edges 56 of thefirst and second tapes 12 a, 12 b define a gap therebetween that iswithin the predetermined offset distance interval. The maximum andminimum values of the interval can be determined according to the affectof gaps and laps on the properties of the resulting composite member 14,the requirements of the composite member 14, and the degree of contourof the surface 18. In some cases, the minimum value of the interval canbe zero or even a small negative value.

The configuration of all of the paths can be determined before some orall of the tapes 12 are disposed on the contour surface 18. That is, theforegoing method of determining the configuration of the paths 50 can beperformed theoretically or numerically, and then the tapes 12 can bedisposed accordingly. For example, the configurations of the calculatedpaths 50 can be stored electronically in a memory 44 of the apparatus10, and the tapes 12 can then be disposed by the apparatus 10 accordingto the calculated configurations of the respective paths 50.

According to one method of manufacturing the composite member 14, thecontour of the contour surface 18 is modeled and stored numerically in acomputer device, e.g., as a plurality of coordinate data valuesrepresentative of points on the contour surface 18 of the mandrel 16. Aprogrammable logic device, such as a computer operating according toinstructions of a computer software program, can be used to calculatethe configuration of the paths 50, and the configuration of the paths 50can be stored for subsequent use in manufacturing the composite member14. For example, the configurations of the paths 50 can be stored as aplurality of coordinate data points that define the paths 50. Thecoordinate data points representing the paths 50 can be stored in adatabase of a computer or in another electronic storage device.Thereafter, the data points, such as stored in the database, can be usedto control the motion of the apparatus 10 for disposing the compositetapes 12 to form the composite member 14. For example, the data pointscan be used to generate instructions characteristic of the motions ofthe apparatus 10, and those instructions can be stored in the memory 44or otherwise provided for controlling the apparatus 10 duringmanufacture of the composite member 14.

As described above, each of the segments 58 of each of the paths 50defines a natural path extending between the points at the opposite endsof each segment 58; however, the segments 58 of each path 50 incombination do not define a natural path. That is, the segments 58 arejoined at non-natural angles. Thus, each tape 12 can be disposed as aplurality of portions, each portion corresponding in length and positionto one of the segments 58. Each tape 12 defines the portionscontinuously. That is, each tape 12 can be continuous and uniform,without breaks or discontinuities between its ends and includes aplurality of the portions between the ends of the tape 12. However,between each pair of adjacent portions, each tape 12 defines thenon-natural angle, where the tape 12 diverges slightly from a naturalpath. Thus, each tape 12 can be slightly stressed at the angles, thoughtypically the tape 12 is not stressed sufficiently to result inwrinkling since the difference in the angle at which adjacent segments(and, hence, tape portions) are disposed is typically relatively smallas described below.

The values of the non-natural angles are a result of the determinationof the configuration of each segment 58 of each path 50. Eachnon-natural angle deviates by an angle that is only slightly offset fromthe angle that would occur in a natural path extending through the samepoint on the contour surface 18. The amount of offset of eachnon-natural angle relative to the natural angle that would otherwise bedefined by a natural path at the same point on the contour surface 18can be limited to a maximum offset angle. The maximum offset anglebetween segments (and, hence, tape portions) can be affected by thecontour to which the tape 12 is to conform, the physical properties ofthe tape 12, the configuration of the apparatus 10, and the like. Forexample, the maximum offset angle can be affected by the width,thickness, and stiffness of the tape 12; the amount of tack orstickiness of the tape 12 and therefore how well the tape 12 adheres tothe underlying layer; the geometric configuration of the compactiondevice of the apparatus 10; and the like. Typically, the maximum offsetangle between adjacent segments 58 (and, hence, tape portions) is lessthan about 3° or 4° and, more typically, less than about 0.5°. In somecases, the maximum offset angle between adjacent segments (and, hence,tape portions) 58 is less than about 0.1° or even less than 0.001°.

Each tape 12 can define any number of non-natural angles and any numberof segments 58 (and, hence, tape portions) therebetween. For example,the number of angles and paths can be determined according to the lengthof each path of each tape, the complexity of the path of the tape, themaximum desired deviation of the tape from a natural path or from thepath of an adjacent tape, and the physical characteristics of thematerial of the tape. In one typical embodiment of the presentinvention, each consecutive portion of each tape has a length that isbetween about 3 inches and 6 feet, such as a length that is betweenabout 6 inches and 3 feet. Thus, in one embodiment, a tape 12 having alength of 18 feet could have between about 3 and 72 consecutive portions(and therefore between about 2 and 71 non-natural angles between theconsecutive portions), or between about 6 and 36 consecutive portions(and therefore between about 5 and 35 non-natural angles between theconsecutive portions). It is appreciated, however, that the differenttapes can define different numbers of portions (and, hence segments 58)and non-natural angles as required for achieving a particularconfiguration.

As described with reference to FIGS. 4-8, the paths 50 of the tapes 12are determined from a starting point 54 between the ends 28, 30 of thecontour surface 18 and calculated in opposite directions outward fromthe starting point 54. The starting point 54 can be a midpoint of therespective path 50. In particular, the location of the starting point 54for each path 50 can be determined according to the midpoint of thepreviously calculated path 50. Alternatively, the starting point 54 canbe positioned other than at the midpoint, e.g., closer to one of theends 28, 30 of the contour surface 18, or even at one end 28, 30 of thecontour surface 18 such that the path 50 can then be determined along asingle direction toward the opposite end 28, 30.

In one embodiment, the starting point 54 is positioned proximate aportion of the path 50 where the tape 12 is likely to overlap withoutmodification to the angles between the segments 58 (and, hence, tapeportions). That is, before the natural path segments 58 for the secondpath 50 b are determined, a natural path can be determined adjacent thefirst path 50 a. Typically, the natural path is not precisely parallelto the first path 50 a. Thus, a transverse distance between the twopaths 50 a, 50 b varies along the length of the paths 50 a, 50 b. Thatis, at one or more portions of the paths 50 a, 50 b, the two paths 50 a,50 b define a minimum transverse distance. The start point 54 forcalculating the configuration of the second path 50 b can be positionedat a point corresponding in position on the contour surface 18 to theportion of the natural path where the minimum transverse distance isdefined. In other words, the starting point 54 for calculating the pathof the second path 50 b can correspond to the portion of the surfacewhere overlap between the tapes 50 a, 50 b would most likely occur ifthe second tape 12 b were disposed along a natural path. It is believedthat the use of such a starting point can result in minimal laps andgaps without using excessive offset angles between successive segments58 of each path 50. In any case, the tapes 12 can be disposedcontinuously from one end 28, 30 of the contour surface 18 to the otherend 28, 30 by the apparatus 10, which traverses repeatedly between thetwo ends 28, 30, laying one or more of the tapes 12 in each pass.

FIGS. 9-11 illustrate the effect of the adjustment of the non-naturalangles between the segments 58 of the paths 50 of the tapes 12. Inparticular, FIG. 9 illustrates a natural or geodesic path over a contoursurface 18. FIG. 10 illustrates a comparison between the natural path ofFIG. 9 and a modified path 50 determined according to the presentinvention, i.e., a path formed of a plurality of natural path segments58, with at least some of the adjacent segments 58 defining non-naturalangles. In particular, the natural path 60 of FIG. 9 includes sevensegments 62 a-62 g that are defined by eight points 64 a-64 h. At thesix points 64 b-64 g between adjacent segments 62 a-62 g of the path 60,the path 60 defines natural angles. Similarly, a modified path 70according to the present invention having seven segments 72 a-72 g isshown in FIG. 10, with points 74 a-74 h. However, the angle between thesecond and third segments 72 b and 72 c is a non-natural angle. That is,the angle is modified from the natural angle by an offset angle 76, andtherefore the path of the segments 72 b, 72 c is modified from thenatural path. In fact, it is shown that a relatively small modificationin the angles can significantly affect the configuration of the path 70.Thus, the gaps and/or laps between adjacent tapes 12 can be minimized,eliminated, or otherwise optimized. In this regard, it is noted that theoffset angle 76 indicated in FIG. 10 is shown to be somewhat larger thantypically employed for purposes of illustration.

FIG. 11 illustrates a further modification to the path of FIG. 10. Themodified path 80 of FIG. 11 includes six segments 82 a-82 f defined byseven points 84 a-84 g. In particular, the modified path 80 omits thethird point 74 c of the path 70 shown in FIG. 10, i.e., the first pointof deviation of the path 70 shown in FIG. 10 from the natural path 60 ofFIG. 9. While not intending to be limited to any particular theory, itis believed that the omission one or more of the points where themodified path first deviates from the natural path can improve thesmoothness of the modified path, thereby possibly reducing stresses inthe tape 12, wrinkling, and/or lapping or gapping between tapes 12. FIG.12 illustrates a tape 90 disposed on a contour surface 18, the tape 90defining portions 92 a-92 f, each of which corresponds to the pathsegments 82 a-82 f of the path 80 of FIG. 11.

The segments 58, 72 a-72 g, 82 a-82 f of the paths 50, 70, 80, and hencethe portions of the tapes 12, can have various lengths. In oneembodiment of the present invention, each of the segments 58 is at leastabout as long as the distance between the supply roll 20 of the tape 12and the roller 24 or other compaction device, i.e., such that any tape12 that has been dispensed from the roll 20 within the apparatus 10 canbe disposed onto the mandrel 16 before the direction of each tape 12 ismodified at a subsequent non-natural angle defined by the respectivepath. Alternatively, if the tape 12 is supported between the roll 20 andthe compaction device, such as by the roller 32 or other supportstructure, each segment (and, hence, each corresponding portion of thetape 12) can have a length that is at least about the distance betweenthe compaction device and the roll 20 or other support structure. Forexample, in one embodiment, each segment has a length that is at leastabout 30 inches.

Each tape 12 typically has a uniform width along its length, i.e., sothat the transverse edges 56 of each tape are linear and parallel to oneanother. However, in some cases, one or both of the edges 56 can benonlinear and/or the edges can be nonparallel. For example, one of theedges 56 of each tape 12 can be trimmed before or during the lay-upoperation. In this way, the tapes 12 can be adapted to furtheraccommodate various contours in the workpiece and/or reduce lapping orgapping between tapes 12. An apparatus and method for slitting orcutting tapes 12 is further describes in U.S. Pat. No. 11/088,288,titled “Apparatus and Method for Composite Tape Profile Cutting,” filedMar. 24, 2005, the entirety of which is incorporated herein byreference.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1. A method of forming a composite member, the method comprising:providing a contour surface corresponding in shape to a desired contourof the composite member for supporting a plurality of elongate tapes ina substantially parallel configuration, each tape including a pluralityof reinforcement members disposed in a matrix material; and disposingeach of the elongate tapes along a path defined by a plurality ofnatural path segments, each segment of a single path being disposed at anon-natural angle relative to adjacent segments of the path, and eachtape comprising a plurality of physically discrete portionscorresponding to the natural path segments and positioned relative toadjacent portions in a continuous, end-to-end manner in a lengthwisedirection so as to define the non-natural angle between adjacentportions without discontinuities between consecutive portions, such thata transverse edge of each elongate tape is disposed within apredetermined offset distance interval from an adjacent one of thetapes.
 2. A method according to claim 1, further comprising determininga configuration of each path by: determining the contour of the surface;determining a first path across at least a portion of the surface; andcalculating a configuration of each natural path segment of a secondpath adjacent the first path, a first end of each natural path segmentof the second path defining an offset angle relative to an adjacentnatural path segment of the second path such that a second end of eachnatural path segment of the second path defines an offset distance fromthe first path, the offset distance being within the predeterminedoffset distance interval.
 3. A method according to claim 2 wherein saidcalculating step comprises calculating the natural path segments withthe offset angle of each natural path segment being less than a maximumoffset angle such that the elongate tapes are configured to be disposedwithout wrinkling.
 4. A method according to claim 2 wherein saidcalculating step comprises calculating the natural path segments withthe offset distance of the second end of each natural path segment beingapproximately equal to a target distance that is less than thepredetermined offset distance interval.
 5. A method according to claim 2wherein said calculating step comprises: calculating the configurationof a first one of the natural path segments of the second path at apoint partially between opposite ends of the second path; andcalculating the configuration of the successive natural path segments ofthe second path in opposite directions from the first one of the naturalpath segments, the second end of each successive path segment definingthe first end of a successive one of the path segments.
 6. A methodaccording to claim 5 further comprising: prior to said step ofcalculating the configuration of the first one of the natural pathsegments, determining a configuration of a natural path adjacent thefirst path; and determining a portion of the natural path adjacent thefirst path defining a minimum transverse distance therebetween, whereinsaid step of calculating the configuration of the first one of thenatural path segments comprises calculating the configuration of thefirst one of the natural path segments at a point corresponding inposition to the portion of the natural path defining the minimumtransverse distance.
 7. A method according to claim 1 wherein saiddisposing step comprises disposing the elongate tapes from a supply rollof an automated tape laying device and pressing the tape against thecontour surface with a compaction device.
 8. A method according to claim7 wherein said disposing step comprises disposing each tape in theplurality of portions, each portion of each tape being at least about alength of the tape supported between the supply roll and the compactiondevice of the automated tape laying device.
 9. A method according toclaim 1 wherein said disposing step comprises disposing the tapes on thesurface substantially without wrinkling of the tapes.
 10. A methodaccording to claim 1 wherein said disposing step comprises disposingeach elongate tape with adjacent portions of the tapes defining anoffset angle that is less than about 4°.
 11. A method according to claim1 wherein said disposing step comprises disposing each elongate tapewith adjacent portions defining an offset angle that is less than about0.5°.
 12. A method according to claim 1 wherein said disposing stepcomprises disposing each elongate tape such that each of the consecutiveportions defines a length between about 3 inches and 6 feet, adjacentportions of each tape defining the non-natural offset anglestherebetween.
 13. A method according to claim 1 wherein said disposingstep comprises disposing each elongate tape such that each of theconsecutive portions defines a length between about 6 inches and 3 feet,adjacent portions of each tape defining the non-natural offset anglestherebetween.